Delhi's ethnic groups are diverse. The Yamuna river's flood plains provide fertile alluvial soil suitable for agriculture but are prone to recurrent floods. The Yamuna, a sacred river in Hinduism, is the only major river flowing through Delhi. The original natives of Delhi are those whose ancestors lived in the Yamuna basin, a region which spreads radially from the capital up to a distance of approximately 200 kilometres. Today the migrant population consists largely of Punjabis, Bengalis and recently,' Biharis. During parts of the British Raj, Delhi was made a district city of the Punjab Province of British India. This province was not ethnically homogeneous and large amounts of Hindi speakers resided in the southeast, now Haryana and Delhi. Caste and politics According to a 2013 The Hindu article, surveys by the political parties indicate that the dominant voter caste / community groups in Delhi include the Jats (10%), Punjabis (9%), Vaish (8%), Gujjars (7% ) and Sikhs (4%). A 2013 The Pioneer report estimates Jats to be only 5.5% of the total electorate. According to another 2013 The Pioneer report, the Brahmins comprise 12-14% of Delhi's population. According to a 2015 India TV article, the major voter social groups include Punjabis (different castes and religions) (35%), Purvanchalis (24%), Muslims (12%), Jats (8%), Vaish (8%), Gujjars (7%), Sikhs (5%) and around 3.5 million Uttarakhandis. According to a 2015 report by The Tribune, Delhi has 81% Hindus and 11.7% Muslims. 35% Punjabi population controls 15-20% vote share in at least 20 constituencies. Purvanchalis, as per the report, were at 4 million. A 2017 article by the Indian Express reported a total of 1.2 to 1.4 million voters who have roots in Uttarakhand. Jats, Punjabi Khatris and Brahmins dominated politics in Delhi for many decades. Numerically high, the ethnic Punjabis are predominantly Hindi-speaking Punjabi Hindus. In the 2015 Legislative Assembly election, 12 out of Delhi's 70 constituencies were reserved for scheduled caste (Dalit) candidates because of dominant Dalit population. Migrants The Indian censuses record the native languages, but not the descent of the citizens. Linguistic data cannot accurately predict ethnicity: for example, many descendants of the Punjabi Hindu and Sikh refugees who came to Delhi following the partition of India now speak Hindi natively. Thus, there is no concrete official data on the ethnic makeup of Delhi. Delhi is an ancient city, and the people residing in the Yamuna River basin were